1. Field of the Invention
The present invention relates to an optical imaging lens assembly, and more particularly to the optical imaging lens assembly comprised of five non-cemented lenses with refractive power to provide a short total length with great image quality for electronic products.
2. Description of the Related Art
In compact electronic products such as digital still cameras and mobile phone cameras, an optical imaging lens assembly is generally installed for capturing images of an object, and the optical imaging lens assembly tends to be developed with a compact design and a low cost, while meeting the user requirements for good aberration correction ability, high resolution, and high image quality.
In general, a conventional optical imaging lens assembly of a compact electronic product comes with different designs, including the two-lens, three-lens, four-lens, and five-or-more lens designs. If the image quality of a compact electronic product is taken into consideration, the optical imaging lens assembly with a design of four or five lens elements has advantages on image aberration and modulation transfer function (MTF) performance, wherein the design with five lens elements having a higher resolution, and is suitable for electronic products that require the high quality and high pixel requirements.
In various compact designs of the optical imaging lens assemblies comprised of five lens elements and having a fixed focal length, the prior art adopts different combinations of positive and negative refractive powers, such as a group of stacked lenses as disclosed in U.S. Publications Nos. US2004/0196571 and US2003/0117722 and a combination of a first lens element with negative refractive power and a second lens element with positive refractive power as disclosed in U.S. Pat. No. 7,480,105. Since two glass lenses are cemented, it is difficult to control the cost for mass production, thus incurring a higher manufacturing cost. In addition, the glass lenses generally have a thickness greater than that of plastic lenses, and aspheric lenses cannot be made easily by glass, and the total length of the optical system cannot be shortened easily. If the first lens element with negative refractive power is adopted, the level of difficulty to reduce the total length of the optical system will be much higher.
In products such as compact digital cameras, web cameras, and mobile phone cameras, the optical imaging lens assembly requires a compact design, a short focal length, and a good aberration correction. As disclosed in U.S. Pat. No. 7,502,181, a fourth lens element with negative refractive power and a fifth lens element with negative refractive power are installed, thus it is difficult to reduce the total length of the optical system. In the description above, the conventional designs will increase the rear focal length and the total length of the optical imaging lens assembly. Therefore, the present invention provides a more practical design to shorten the optical imaging lens assembly, while using a combination of refractive powers of five lens elements and a combination of convex and concave optical surfaces, wherein the fourth lens element and the fifth lens element have positive refractive power and negative refractive power respectively, and this complementary combination with a telecentric effect is favorable for reducing the rear focal length and the total length of the optical imaging lens assembly effectively, and further improving the image quality and applying the optical imaging lens assembly to compact electronic products.